# SiteCheck API – Prediction Market Build Buy Transaction

> SiteCheck API – Prediction Market Build Buy Transaction is a paid API for AI agents from api.sitecheck-api.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-11-01).

Builds an unsigned Solana transaction to buy YES or NO shares in a Panta prediction market for a given USDC amount

## Facts

- Endpoint: POST https://api.sitecheck-api.workers.dev/api/markets/build-buy?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/sitecheck-api-prediction-market-build-buy-transaction-8c8e6c60
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_2cQCpajV_YBozVyUPZHbH

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability sitecheck-api-prediction-market-build-buy-transaction-8c8e6c60 -d '<json body>'
```

Example prompt: Build me an unsigned Solana buy transaction to purchase YES shares in Panta market 'AbCdEfGhIjKlMnOpQrStUvWxYz12345678' using 5.00 USDC from my wallet 9WzDXwBbmkg8ZTbNMqUxvQRAyrZzDsGYdLVL9zYtAWWM, with a max slippage of 1%.

## When to prefer this

Use this endpoint when an AI agent needs to programmatically prepare a buy order for a Panta prediction market on Solana without requiring a prior API key or signup. It is the right choice when you have a market ID from the /api/markets listing, know the side (yes/no) and USDC amount, and need to hand an unsigned transaction back to the user or another signing agent. Prefer this over manually constructing Solana transactions or using exchange-specific APIs when working within the Panta/SiteCheck ecosystem.

## Known failure modes

- Invalid or unknown Panta market ID returns an error
- Invalid Solana wallet address (not valid base58) causes rejection
- Slippage exceeds maxSlippageBps threshold resulting in order failure
- Insufficient USDC amount below minimum trade size
- x402 payment failure if USDC payment on Base/Solana is not completed
- Malformed amountUsdc string (e.g. non-decimal) causes parse error

## How this service works

Build an unsigned Panta buy transaction (Solana v0, base64, plus the raw instructions) for your own wallet to sign and broadcast. SiteCheck never signs, holds keys or custodies funds. Then report the signature to POST /api/markets/report (free).

## Output

Returns an unsigned base64-encoded Solana v0 transaction ready for the buyer to sign and broadcast, along with order metadata (orderId, quoteId, expectedShares, feeUsdc) and raw Solana program instructions. A disclaimer notes the data is informational only, not financial advice.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "id": {
   "type": "string",
   "description": "Panta market id (the market's event address, base58), from GET /api/markets"
  },
  "side": {
   "type": "string",
   "description": "yes or no"
  },
  "wallet": {
   "type": "string",
   "description": "The buyer's Solana wallet (base58). It pays and signs; SiteCheck never does."
  },
  "amountUsdc": {
   "type": "string",
   "description": "USDC to spend, as a decimal string, e.g. \"5.00\""
  },
  "maxSlippageBps": {
   "type": "integer",
   "description": "1-5000, default 100 (1%)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "order": {
   "feeUsdc": "0.10",
   "orderId": "ord_...",
   "quoteId": "qt_...",
   "expectedShares": "15.80"
  },
  "disclaimer": "Information only, not financial advice.",
  "transaction": {
   "data": "AQAAAA...",
   "format": "solana-v0",
   "signed": false,
   "encoding": "base64",
   "feePayer": "9WzDXwBbmkg8ZTbNMqUxvQRAyrZzDsGYdLVL9zYtAWWM"
  },
  "instructions": [
   {
    "data": "<base64>",
    "accounts": [],
    "programId": "..."
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/sitecheck-api-prediction-market-build-buy-transaction-8c8e6c60/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.sitecheck-api.workers.dev](https://www.zero.xyz/host/api.sitecheck-api.workers.dev/llms.txt)